Abstract
We determine the complex-valued solutions of the following extension of the Cosine–Sine functional equation
where S is a semigroup generated by its squares and \(\sigma \) is an involutive automorphism of S. We express the solutions in terms of multiplicative and additive functions.
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Ajebbar, O., Elqorachi, E. The Cosine–Sine functional equation on a semigroup with an involutive automorphism. Aequat. Math. 91, 1115–1146 (2017). https://doi.org/10.1007/s00010-017-0512-9
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DOI: https://doi.org/10.1007/s00010-017-0512-9